Will Wolbachia help defeat dengue?

One of the Wellcome Trust’s areas of focus for research funding is combatting infectious disease.  We have recently agreed a strategic award of over £7.5 million to continue development of an effective and sustainable approach to reducing the transmission of dengue fever. The research is an international collaboration and project leader Professor Scott O’Neill, Monash University, Australia explains its importance…

Dengue fever is ranked by the World Health Organization (WHO) as the most important mosquito-borne viral disease in the world. With an estimated 390 million dengue infections annually, leading to tens of thousands of deaths, the hospitalisation of millions creates extremely high social and economic costs in developing countries.

It has to be stopped.

While others are working on vaccines and cures, we are working on what we hope will be a control method to support these initiatives and greatly reduce this rapidly spreading disease.

We – that is members of the Eliminate Dengue research program – are working with Wolbachia, an extremely common bacterium that is found in the majority of insect species, but not the dengue-transmitting mosquito Aedes aegypti. We have found that when the bacterium is introduced into the mosquito the dengue virus can’t grow as well – and if it can’t grow, it can’t be passed between people. We also found that the mosquitos with Wolbachia passed the bacterium to their offspring – and this set us buzzing.

While the target of our work is no bigger than a mosquito, moving from the microscope to over 100 dengue endemic countries is no easy ask of normally lab-restrained scientists. And, while we had great expectations of the science, how would we (and could we?) replace wild mosquito populations with Wolbachia mosquitoes and their dengue blocking progeny?

One thing we did know was that we certainly couldn’t do it on our own. We needed support not only from governments and regulators, but also householders in dengue prone communities.

If I came and knocked on your door to ask if you’d let me release mosquitoes with a bacteria that we’d introduced – in a lab – into your home, to feed on you and your family’s blood, would you welcome us in?

If you overcame your initial desire to shoo us away, you’d probably have a few questions you’d like to ask before you gave us your consent. These would probably be the same questions as residents in Cairns, far northern Australia, Yogyakarta, Indonesia and Tri Nguyen Island, Vietnam had. Thankfully we are able to answer them sufficiently well that we are currently releasing Wolbachia mosquitoes and conducting trials in all these communities.

While we are already seeing success in these trials with close to 100% of mosquitoes found in the 2011 Cairns field trial sites still carrying Wolbachia over three-years after our last controlled release, observing reduced dengue transmission is our ultimate goal.

In 2005 we were fortunate to be awarded funding by the Grand Challenges in Global Health initiative of the Bill & Melinda Gates Foundation which has enabled us to meet some amazing and, some unexpected, milestones in our research. With continued support from the Foundation, and now funding from the Wellcome Trust, we are about to enter the most important phase of our research – investigating the impact of the method in reducing the prevalence of dengue disease in endemic countries.

Following extensive government and community support, next year we hope to begin undertaking citywide trials in Yogyakarta and Nha Trang, Vietnam to compare dengue incidence in susceptible individuals who reside in areas with and without Wolbachia mosquitoes.

While we’re carrying out this engagement in south-east Asia, we are also preparing for a large trial in Townsville, northern Australia to begin later this year. This trial will allow us to develop our community engagement activities and refine the most cost-effective and efficient methods for the deployment of the Wolbachia control method across larger urban areas.

Entomological studies and community engagement activities from collaborating project members are also advancing in Rio de Janeiro, Brazil and Medellin, Colombia. With local government approval and community support it is also hoped to begin field trials in these cities in 2014/2015.

I invite you to join the Wolbachia buzz and follow our research through progress updates on our website – EliminateDengue.com

You can put your questions to members of the Eliminate Dengue team via their website or subscribe to the programme newsletter – the current issue can be found here. We also have a short video about the research that we invite you to watch on the site.

Part of the Wellcome Trust’s vision is to combat infectious disease by finding new ways to prevent and treat bacterial, viral and parasitic diseases that kill millions of people worldwide. This funding to help continue development of sustainable dengue reduction measures is from a Wellcome Trust Strategic Award. You can find details of all our available grants an funding schemes on the funding pages of the Wellcome Trust website and keep up to date by following us on Twitter.

Image credits: Adult female Ae. aegypti mosquito - Liverpool School of Tropical Medicine courtesy of A Stich, Wellcome Images, all others courtesy of Eliminate Dengue.